Joint



Sept. 19, 1944.

J. N. HELTZEL JOINT Filed Jan. 9, 1940 2 sheets-shea 1 'lll/l j sept.-19, 1944. J. N. HELTZEL 2,358,328

JOINT Filed Jan. 9, 1940 2 Sheets-Sheet 2 v n., f, a

Patented Sept. 19, 1944 yUMTED STATES PATENT oFFica JOINT a John N.Heltzel, Warren, Ohio Application January 9, 1940,'serial1v0. 313,128

(o1. :i4-1s) 5 Claims.

This invention relates to improvements in joints and joint installingapparatus for concrete roads, floors, walls, revetments, and otherstructures constructed of plastic setting material. The presentapplication is a continuation in part of my copending application SerialNo. 708,155, filed January 24, 1934.

Modern traflic conditions on highways have necessitated an increased useof load transfer members bridging joints, either longitudinal ortransverse, between the concrete slabs from which such highways areprincipally constructed. The problem is not solved by the mere additionof load transfer dowels, such as commonly employed. for the shrinkage ofplastic concrete when drying sets up a frictional 'drag on the imbeddeddowel bars, with the consequent breaking of the concrete at pointsremote from the joints between the slabs. It ha-s been found, also, thatwhere dowel bars alone are depended upon, there is an inevitable warpingof the concrete slabs which tends to bend the dowel bars. This bendingprevents restoration of the slabs to their initial condition on thesubgrade and in addition, there is a constant breaking away of concreteor falling off of the material at the faces of the concrete slabs in theareas surrounding and adjacent to the dowel bars.

An object of the present invention is to provide improved means forproducing joints in concrete roads and the like, utilizing dowel meansin which friction with respect to the surrounding concrete is reduced toa minimum by a novel structure of dowel and bearing therefor.

Another object is to provide, in such joints, means to eliminate tensionin the concrete itself and to conne such tension directly to the dowelmeans constituting load transfer elements extending between therespective slabs.

Another object is to provide an improved dowel bar construction -andinstallation therefor, in

- which the dowel assembly is provided with stress reducing meansextending appreciably into the body of the surrounding concrete in therespective slabs between which a joint is formed.

A further object. is to provide a dowel assembly having means forautomatically positioning the dowel members at right angles with respectto the joint forming member with' which the dowel means is associated inproducing a joint.

A still further object is toprovide in a dowel assembly and in a roadjoint installation, means for transferringvertical load strain to thedowel means by the employment of shear plates associated with thedowels.

Still another object is to provide insuch constructions, means forautomatically eecting relative shift between cooperating dowel membersassociated with spaced concrete slabs in the formation of a joint as thegreen concrete shrinks in the process of drying out, therebycompensating for the shrinkage and relieving the slabs from frictionalstrains.

Other objects will become apparent from the description.

In the accompanying drawings:

Figure l is a perspective view of a shear plate and dowel construction,and illustrating the use of plural dowel elements in connection withsocket means carried by shear plates.

Figure 2 is substantially a fragmentary vertical section through a dowelbar housing of the type employed in the installation shown in Figure 1.

Figure 3 is a perspective view of another embodiment of jointconstruction and illustrating the use of shear plates of differentrelative sizes associated with dowel means and stress reducing elementsconnected with marginal reinforcing means for supporting the jointassembly on a subgrade during pouring oi the concrete.

Figure 4 is a vertical section through a joint, illustrating a furtherembodiment of shear plate and dowel construction in which the dowelsocket is provided with means for expanding the A-shear plates inopposite directions to compensate for shrinking of concrete while it isdrying out.

Figure 5 is a perspective view of still another type of jointinstallation embodying an alternative construction of shear plate andintegral dowel means and socket therefor.

Figure 6 is a vertical 'section through a joint illustrating a differenttype of shear plate and dowel assembly in which the dowel is floatedupon anti-friction bearing means housed within the dowel receivingsocket.

Figure '7 is a perspective view illustrating a further modification ofthe dowel bearing'arrangement generally disclosed in Figure 6, anddetailing a different type of dowel housing and anti-friction supporttherefor.

plates, stress reducing elements. etc., as -well as' force to 'insure anexpanding separation of the shear plates carrying the dowel and thedowel socket during the pouring of the concrete forming the slabs withwhich they are associated. It has been found that concrete shrinksconsiderably in dryingV out and the contraction resulting, if resistedby the frictional binding engagement against immovable doweling means,very often causesa rupture in the concrete at 19.' points remote fromthe joint. In order to comever a particular illustration or referenceismade to a particular type of joint, the structure disclosed mayequally as well be employed in connection with other types of jointinstallation as above noted.

Figure 1 illustrates an application of the invention which involvesshear plates having plural dowel and socket means associated therewith.In this form each shear plate 236 and 291 has rigidly secured thereto arearwardly projecting dowel socket indicated at 299 and 299respectively. The plate 293 is formed with an integral laterally andinwardly directed base flange 293 which seats upon the subgrade andwhich is upwardly and outwardly reverted upon itself as at 29| toprovide a relatively xed base which extends up into the material of theconcrete slab with which the plate is associated. The dowel socket 233is disposed slightly above the base portion 29| and is' located adjacentone side edge of the plate. At its opposite side edge, and substantiallyin the horizontal plane of the dowel socket, theplate 239 has rigidlysecured thereto an inwardly projecting stress reducing member 292 havingan upwardly and rearwardly inclined extension adapted to be embedded inthe body of the concrete slab and to transmit strains remote from thejoint directly to the shear plate. 'I'he member 292 is passed throughthe plate to provide a dowel portion, not shown on. account of the angleof the perspective, which extends transversely across the joint spaceinto slidable housing engagement within the dowel socket 299 carried bythe opposite shear plate 291. This latter shear plate is' likewiseprovided with a stress reducing member 293 having an angled extensionsimilar to that of the member 292, and

wardly pressed to provide a conforming socket.

means 299 which is arranged to receive the ribbing on the oppositeplate. The shear plates at their upper edges are provided withrearwardly directed top nanges which are corrugated or recessed as at291 to provide for an anchorage of the flanges in theV body of theconcrete.

Figure 2 illustratesa detail of the dowel and socket assembly used inthe embodiment shown 'mineure 1. mtmscasetnesoekeasuenasm,

is welded to the-rear face of the associated shear plate 233and'receives the dowel 394 in slidable engagement. Spring tension means,here shown as a coiledexpansion spring 299,-is disposed in the socketbetween the socket end and the end of the dowel bar. The'resilientmeansis normally underV tension constantly urging the dowel bar outwardly ofthe socket with just sumcient pensate for this and to keep the shearplates in tight binding engagement against the plastic concrete whilethe concrete is drying out, a spring means 293 is provided-which insuresthat the shear plates shall -be gently but firmly forced up against thegreen concrete under tension throughout the period in which it isdrying. When the slabs expand and move toward one another the dowel is,of course, projected further into the socketv and this movement willthen be resisted by compression of the Spring. Providing a cushioningeilect between the dowel and its socket. v

Figure 3 illustrates an embodiment of the invention in which the shearplates are of diil'erent relative sizes and in which only one assemblyof dowel and socket is utilized. In this form the larger shear plate 33|is formed withan intumed base flange 332 which seats upon the subgrade.A similar flange 333 is formed at the upper edge of the plate andextends back into the body of its associated concrete slab somewhatbelow the top surface thereof, it being apertured for anchorageengagement with the concrete.

The shear plate V33| carries on its inner face a v rigidly attacheddowel socket member 334 disposed at the upper portion of the plate andhaving at its inner end an integral downwardly and rearwardly inclinedstress reducing extension y 339. The lower end of the extension 335 isconnected with an angle member 336 seated on the subgrade in spacedarrangement inwardly from the shear plate 33| and extendinglongitudinally of the joint. Preferably the connection is made byextending the ends of the member 335 through an aperture provided forthe purpose in the upstanding flange of the angle member; however, anysuitable form of connection may be employed. At one side the dowelsocket member 334 is welded or otherwise rigidly connected to acompanion stress reducing extension 331 that is rigidly secured at itsouter end to the inner face of the shear plate and which is upwardly andrearwardly inclined at its inner end portion to provide reinforcementfor the concrete slab and to transmit distant strain directly to theshear plate. therethrough a marginal reinforcing bar 339, the bar beinganchored in its receiving slot by means of the wedge pins 339. Thereinforcing bar 333 and its connection may be dispensed with as it isnot necessary to the operative organization of the joint. In thisembodiment the dowel socket contains a resilientmember 349, preferably arubber pad, although it may be an expansion spring, which bears againstthe inner end of the dowel bar 34| to provide a cushioning element aswell as a meansfor normally urging the bar outwardly with respect to thesocket.

The dowel bar 34| is rigidly mounted in a supporting member 342 andrigidly secured on the inner face of the shear plate 343 which isdisposed on the opposite side of the joint strip 344. The plate 343is'relatively smaller than the plate 33| and is supported in positionabove The extension 331 is provided to receive` outward from its centralportion.

the subgrade by means of the extension 342 which corresponds in shapeand function to the mem-ber 334 associated with the shear plate 33|. Theextension 342 is likewise connected at its lower end to al companionangle member 338 seated on the subgrade and extending longitudi-V nallyof the joint. Also, the shear plate 343 has rigidly secured to its innerface a stress reducina member 345 which corresponds in shape andfunction to the stress reducing member 331 and which may likewise beassociated with the marginal reinforcing bar 338 secured by the Wedgepin 339 in the slot provided for the purpose within the extension. Inthis embodiment the two shear plates are held firmly against oppositefaces of the joint strip during pouring of the concrete by means of atie wire 326 passed through the upper edge portion of the joint stripand tied into anchorage apertures provided in the respective top flanges341 and 333 of the shear plates. After the concrete has set the tiewires 326 maybe clipped and the Joint finished in the usual manner. Ifdesired the plates may be connected by employing connector clips.

In the embodiment illustratedA in Figure 4 the shear plate 391 embeddedin the face of the concrete slab at one side of the joint strip 398carries a dowel bar 399 whose inner end is bifurcated.

to provide stress reducing extensions 400 and whose outer end isprovided with an enlarged head 40| slidably received in a dowel socketmember 402 that is welded to the inner face of the opposite shear plate403. The dowel bar 399 is passed through the shear plate 391 and iswelded thereto to provide a rigid connection between the parts. In thisform of the invention the dowel bar has a slidable bearing through anaperture provided therefor in the shear plate 403 which carries thedowel socket, and the enlarged head 40| bears against a. member 404formed of resilient material, here shown as a block of rubber, but whichmay be an expansion spring or other suitable resilient means, disposedwithin the dowel socket. As the concrete sections move toward oneanother in expansion the thrust of the dowel bar within its socketis-resisted by the compressible resilient member 404 which provides acushioning means. In the setting of the concrete from which the slabsare formed and while the material 'is yet green, the resilient member404 exlerts an expanding tension against the dowel bar head 40| whichforces the dowel bar outwardly with respect to its socket tending toseparate the shear plate 391 from the shear plate 403. This separatingforce is sufficient tomaintain the two shear plates firmly engagedagainst the concrete so that the plates move back in accordance with theshrinking of the concrete and there will be no pulling away of thematerial from around the plates. It is to be understood that in thisembodiment, while the concrete is being poured, a suitable tie means isprovided to hold the shear plates firmly against the opposite faces ofthe joint strip', and this means is removed after the concrete hassetsufiiciently to permit same.

In the form shown in Figure 5 the shear plate 421 has an integral dowel438 placed laterally The shear plate 421 is embedded in the base of itsassociated concrete section and has its top flange 429 rearwardlydirected somewhat below the top face of the concrete and apertured as at430 for anchoring engagement with the concrete. The

. Both flanges are apertured in vertical alignmentto receive theinturned terminal portions of the to the top flange and seats upon thesub-grade.

arms of av substantially U-shaped reinforcing member 432- which isdisposed vertically in embedded relation within the concrete of theassociated slab and rearwardly ofthe shear plates.

' The bottom arm of the reinforcing member is maintained in positionupon the subgrade lby means of a stake. or other suitable securing means433. The opposite shear lplate 434 is provided with similar top andbottom flanges and is likewise equipped with one of the reinforcingmembers 432 also secured by a stake 433 and directed oppositely tothemember associated with the shear plate 421. These reinforcing membersact to maintain the shear plates properly positioned upon the subgradeas well as serving as reinforcing members for the body of the concreteslabs in which they are disposed. The shear plate 434 is laterallypressed at its central portion to provide an integral socket 435 whichreceives the dowel 428 of the opposite plate in slidable engagement fortransferring vertical loads across the joint from one slab to the other.The socket also carries a, resilient member 436 such as a block ofrubber or a spring or the like which provides a cushion resisting themovement of the dowel into its socket and which at the same timenormally tensions the dowel to movement out of its socket. By means ofthe resilient member 431i the shear plates, during the drying period ofthe concrete, are gently but firmly urged apart so that they will remainin full bearing contact against the concrete faces of the slabs in whichthey are embedded and vwill move in correspondence with the'shrinkage ofthe concrete. Y

In the type of joint shown in Figure 6 the dowel plate 413 has weldedthereto a dowel bar 414 which is passed centrally therethrough andwhich, in rear of the shear plate is bifurcated to provide arms 415which extend into the material of the associated concrete slab to act asstress reducing elements and reinforcing means. The dowel bar passesfreely through an aperture provided therefor in the opposite shear plate416; the aperture being larger in diameter than is the dowel bar so thata sufficientI clearance exists to permit free. movement of the dowelbal'. The plate 418 is provided on itsrear face with a flxedly connecteddowelA socket 411 which receives the end of the dow'el bar and whichcontains between the laterally enlarged head 418 at the end of the dowelbar and the end of the socket a. coiled ,expansion spring 419 which isbacked by a pad 480 of rubber or rubber resilient material. The springerthe combined resilient means acting against the enlarged head. 418 ofthe dowel bar tends to force the bar outwardly of the socket and' thusto communicate to the shear plates 413 and 414 the lateral expandingaction tending to separate the two. As the concrete of their associatedslabs driesl it shrinks and by virtue of the arrangement of theresilient means within the dowel socket the shear plates 4 will be givena positive movement in the direction bottom aange 43| is lnturned lnparallel relation 76 of shrinkage of the concrete so that they will bekept firmly forced against the faces of the sections in which they areembedded. In this form of the invention the end of the dowel bar whichis housed within the socket is supported on antifriction rollers 48|which are disposed between position.

being necessarily larger than the diameter of the head 418, it followsthat an annular flange 482 will exist on the shear plate around thedowel bar where it passes through the shear plate 416.

The flange serves to retain the lubricant within the socket member andfurther acts as a stop or raceway which retains the roller members 48|ln In this type of joint the Joint space may be sealed at its bottom bya suitable plastic setting sealing medium 488 and, where no joint stripis employed, it may be sealed at the top by a metal insert 484 ofV-shaped form which is forced between the shear plates and whichsupports a body of moldable material 488 at the dividing line betweenthe top faces of the joint slabs. l

Figure 7 illustrates a further embodiment of the principle disclosed inFigure 6. In the form shown in Figure 7 the shear plate 488 at one sideof the Joint has a substantially rectangular cross section dowel bar 481-passed centrally therethrough and welded to the rear face of the plate.'I'he dowel bar 481 at its rear end has suitably secured thereto arearwardly extending reinforcing element in the form of a substantiallyU- shaped bar 488 which is connected to the upper edge of the dowel barand, if desired, a second and similar bar 489 is rigidly secured to itsunder face. These bars extend well back into the body of the concreteforming the slab with which they are associated to serve as stressreducing elements as well as reinforcing means. The dowel bar extendstransversely across the joint space and through an enlarged apertureprovided therefor in the opposite shear plate 498, which plate hasextending from its rear face a dowel socket member 49| which may alsohave secured there to reinforcing members 492 and 493 which aregenerally similar to the members 488 and 489 at the opposite side of thejoint. Atits inner end the dowel.socket.49| is closed by a verticalplate 494 which supports internally thereof a resilient member 495, hereshown as a rubber block or pad, which bears against an enlarged head 496on the inner end of the dowel bar within the socket. In this embodimentof the invention the portion of the dowel bar which is housed within thedowel socket is transversely grooved at itstop and bottom faces toprovide a socket 491 which seats upper and lower arcuaterocker members498 that function as anti-friction bearings for the ilxed dowel barwithin the socket members. These rockers are provided with arcuate outersurfaces which bear against the top and bottom portions of the dowelsocket so that they oscillate on horizontal axes in accordance with therelative movement of the dowel bar and its socket.

Figure 8 illustrates the position of the parts shown in Figure 7 whenthe concrete sections have expanded to approximately their maximumposition with the dowel bar housed to its fartht extent within thesocket. It will be noted that the rockers 498 are tilted on their axes.

1. In a joint for concrete sections, load transfer means bridging thejoint and extending into the sections in xed relation to one andslidable freely at all times in the other, a load bearing -plate in eachsection face and supporting said load transferV means, a housing forsaid load transfer means fixed to the bearing plate in the section iinwhich said transfer means is slidable, and resilient means in saidhousing engaging the load transfer means under tension normally urgingthe transfer means outwardly of the housing.

2. In a joint for concrete sections, a load bearing plate in eachsection face, dowel means extending through and between said plates intothe sections, said dowel means being ilxedly embedded in one section andfixed to the bearing plate in that section and'being slidable freely atall time in the other bearing plate and section, said other bearingplate having dowel socket means xed thereto, and resilient meanstensioned between a portion of said socket and the dowel and normallyurging separating movement between the bearing plates.

3. In a joint for concrete sections,` shear plates embedded in theopposed section faces, a dowel member rigidly secured to one plate andslidable freely at all times through an aperture provided in the other,a socket secured on the inner face of said other plate and housing thefree end portion of said dowel member entirely out of contact therewith,anti-friction bearings in said socket and supporting the end portion ofthe dowel member, and resilient means between a portion of said socketand the dowel member and normally urging the dowel outwardly of thesocket.

4. In a joint for concrete sections, shear plates embedded in theopposed section faces, a dowel member rigidly secured to one plate andfreely slidable through an aperture provided in the other, a socket onsaid other plate and housing the free end of the dowel member, andmovable anti-friction bearings between said dowel member and the socketand supporting the dowel member therein.

5. In a joint for concrete sections, shear plates embedded in theopposed section faces, a dowel member rigidly secured to one plate andfreely slidable through an aperture provided in the other, a socketfixed on said other plate and housing the free end of said dowel memberentirely out of engagement therewith, said free end of the dowel memberhaving opposed arcuate recesses therein, rocker members having roundedends bearing in said recesses, and said rocker members having enlargedarcuate heads bearing on the socket walls, the rocker members comprisingthe sole support of the dowel member the socket.

JOHN N. HELTZEL.

